Re: output of JB in mV?
I don't know that you can use the numbers to make an accurate comparison. To do so would requre Duncan and DiMarzio to do identical tests, exciting the pickup in exactly the same way.
I'm sure someone on here knows the number, though. There are probably a few people that have used both pups and can tell you from experience which one is hotter.
Edit: ranalli beat me to it.